The present invention is directed to a tool that can be placed into rotation, and is suitable for high-speed drive. The tool is capable of having a coolant externally supplied to it and comprises a shaft for holding the tool in a suitable chucking mechanism of the drive at one end of the shaft and comprises a tool head with an active work surface at the other end of the shaft.
Tools which are required to have a relatively great chip-removing power and which operate at extremely high speeds must be adequately cooled. To this end, it is standard to conduct a suitable coolant, usually water or what is referred to as "drill water", onto the tool and to, thus, cool the surfaces to be processed and the working surfaces of the tool as well.
East German Patent DD-267 692 A1 discloses a cutter of a rotating, chip-removing tool that has a comparatively large diameter, for example a knife head for a milling machine. This tool is cooled in that the coolant is sprayed into an annular space in an intentional fashion proceeding from a back side of the tool. Radially extending webs are located in the annular space, and these webs respectively project into the annular space behind the admission opening of the delivery channel as viewed in the rotational sense of the tool. Further conveying of the coolant occurs via a plurality of channels proceeding from the annular space, and these channels proceed from the shaft obliquely outward to the cutters placed at the periphery. The feed point, thus, has a smaller diameter than the exit location at the blades. An increased pressure that drives the coolant outward occurs due to the cross sectional constrictions and also is promoted by the centrifugal force upon rotation of the tool. This type of coolant guidance is relatively complicated, is only suitable for tools having a larger diameter and, due to the design, is suitable for only one rotational sense.
Technica 20/1980, p. 1762, discloses a drill having a cooling channel to continuously cool the main cutters of the drill. The cooling liquid is conducted under pressure into the cutter region proceeding from the tool shaft. The feed of the cooling liquid occurs either by a delivery ring arranged at a shaft end, and this conducts the cooling liquid into the inner cooling channel of the drill and, thus, directly into the cutter region, or the shaft may be provided with a central feed channel and lateral channels departing therefrom via which the cooling fluid is conducted into the cutting region. Here, too, the coolant is conducted via inwardly disposed channels.
In the dental field, tools are employed which have externally applied coolant for drilling, milling, grinding and polishing. These tools are operated in a speed range of up to 30,000 rpm. A water/air mixture is usually supplied for cooling the tool and the preparation area as well. However, this water/air mixture forms a fine fog around the tool tip as a consequence of the turbulence caused by the tool.
Adequate cooling is not assured in tools of the traditional type, particularly given the great stress on the tool as a result wherein premature wear of the tool and/or an inadmissible overheating of the material to be processed can occur.